Power generator and system comprising it

ABSTRACT

A control unit ( 5 ) for controlling each device which constitutes a electric power generator set ( 1 ) is provided with an operation-and-display device ( 28 ) so constituted as to calculate each electric power value data and each electric energy data on external electric power, generated electric power, and load electric power on the basis of sensed data on each value of external electric power and generated electric power transmitted from inverters ( 6   a,    6   b ) and as to store these calculated data and the sensed data, and connected to the electric power generator set ( 1 ) by wires or radio. A cogeneration system comprising the electric power generator set ( 1 ) is so constituted that data on the electric power generation current value of the external electric power source and the electric power generator set ( 1 ) and data on water-heat energy are sensed and transmitted to the control system ( 2 ), and that the control system calculates data on an external electric energy, a generated electric energy, a load electric energy, a water-heat energy recovery quantity, and an energy efficiency to display the calculated data on the operation-and-display device ( 28 ).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an electric power generator set havinga generator driven by an engine and having an ability of interconnectingwith an external electric power supply. Furthermore, the presentinvention relates to an electric power supply system comprising theelectric power generator set.

BACKGROUND ART

Recently, an electric power generator set comes to be used for supplyingelectric power consumption apparatuses (loads) with electric power,wherein the electric power generator set can connect a circuit ofelectric power (internal electric power) generated by a generator drivenby a private engine to an external electric power system line typicallysupplied by a commercial electric power supply, such as an electricpower company.

An internal combustion engine, such as a gas engine or a diesel engine,is applied as the engine for driving the generator of the electric powergenerator set.

The electric power generator set comprises an inverter for supplyingelectric power to the load so as to bring the total of electric powergenerated by the generator and external electric power into agreementwith the electric power demanded by the load. Such an electric powersupply system having a system line of electric power generated by thegenerator in interconnection with the external electric power systemline is referred to as an interconnection system.

On the other hand, recently, a cogeneration system is widely used as anapplication with the electric power generator set having theabove-mentioned interconnection system, which recovers waste heatgenerated from the generator generating electric power so as to supplyhot water by using the recovered heat.

The reason why the interconnection system employs the cogenerationsystem having both heat and electric power produced from an engine is toefficiently and economically use fuel (gas, light oil or the like) fordriving the engine. Therefore, it is preferable that the system alwaysensures efficiency in outputting the heat and electric power to beconsumed regardless of demand status thereof.

In addition, in the light of economic efficiency (energy efficiency) ofthe cogeneration system, it is preferable that the rate of generatedelectric power in the demanded electric power (load electric power)becomes large as much as possible and demand of water-heat energy islarger than water-heat energy generated by the cogeneration system.

However, the energy efficiency of the cogeneration system changescorresponding to energy consumption status of a user, so that the usermust manage operation status of the cogeneration system and collects andanalyzes data for calculating energy efficiency so as to grasp theoptimal conditions of operation. Such complicated collection andanalysis of the data prevents the user from easily and quantitativelygrasping the reduction amount of energy cost (cost merit) as the benefitof introduction of the cogeneration system.

As understood from the above example of the conventional electric powersupply system employing the cogeneration system, the conventionalelectric power supply system combines external electric power andgenerated electric power in efficient rate so as to supply the combinedelectric power, however, it is not sufficiently user-friendly because itdoes not clarify its usage pattern. The electric power system would begreatly satisfying for the user if it clarified the usage pattern ofexternal electric power and generated electric power caused by it.

A well-known conventional mode of the above-mentioned electric powersystem is a package type electric power system having a plurality ofparallel-connected electric power generator sets each of which comprisesan engine, a generator, an inverter and a control unit so that each ofthe electric power generator sets outputs electric power via itsinverter so as to input it into the external electric power.

In the package type electric power system, the control units of therespective electric power generator sets interconnect with one anotherso as to control output of each electric power generator set and thenumber of the electric power generator sets in operation, therebycontrolling output of the whole package type electric power system.

With regard to output control of the whole package type electric powersystem, the control unit of specific one of the electric power generatorsets serves as a master unit centralizing control over the otherelectric power generator sets (control units). The inverter in thespecific one electric power generator set detects electric current fromthe commercial electric power system, and the control unit as the masterunit controls outputs of the control units of the other electric powergenerator sets on the basis of detected results.

However, in the conventional electric power system of the parallel inputtype, only the specific electric power generator set detects theelectric current from the commercial electric power system so that eachof the electric power generator sets other than the specific one cannotfunction as the master unit because its inverter does not detect theelectric current.

Therefore, the specific electric power generator set must be constantlyoperated to control the output on the basis of detection of currentvalue of the commercial electric power system, thereby causing problems,such as its operation time and frequency unevenly larger than the otherelectric power generator sets and short period of its consumable parts.Furthermore, at the time of maintenance of the specific electric powergenerator set, the other electric power generator sets must be alsostopped (because the other electric power generator sets cannot controloutput), whereby the generated electric power cannot be supplied at thetime of maintenance.

SUMMARY OF THE INVENTION

According to the present invention, an electric power generator setcomprises: an engine; a generator driving by the engine; and an inverterhaving an ability of interconnecting the generator with an externalelectric power supply. The electric power generator set comprises: meansfor detecting information concerning electric power of the externalelectric power supply and electric power of the electric power generatorset; means for calculating electric powers of the external electricpower supply and the electric power generator set, electric power to aload, and the respective electric energies; and means for registeringeach of the calculated electric powers and energies. Accordingly, theelectric power generator set can provide charts representing respectiveelectric energies and the like to a user. Furthermore, the electricpower generator set has image-displaying means for displaying a diagramof the respective electric energies. Accordingly, the user of theelectric power generator set can feel a glow of satisfaction at theability of monitoring the electric energy generated by the generator andrealizing the effect of his/her purchased electric power generator set.

For example, a user can compare the commercial electric energy with thegenerated electric energy at each established period, e.g., daily,monthly or yearly. In addition, an expense for the commercial electricpower can be compared with that of the generated electric power.Therefore, the user can compare the running cost of the generatedelectric power with the cost for purchasing the commercial electricpower so as to confirm running merit of the electric power generatorset. Furthermore, the operation-and-display device calculates how longtime is required for recovering cost of equipment investment of theelectric power generator set on the basis of the running merit of theelectric power generator set (the purchased electric power cost minusthe running cost) and displays the result to the user. The respectiveelectric powers and energies are displayed corresponding to theconceptual diagram so that the user can feel a glow of satisfaction atthe ability of easily grasping power supplying pattern of the respectiveelectric power systems and easily comparing the respective electricenergies in image.

Preferably, the above-mentioned electric power generator set maycomprise means for calculating fuel consumption of the engine, andimage-displaying means for displaying the respective electric energiesand the fuel consumption in a table. In this case, if the control unitpreviously stores information concerning the unit cost of fuel, a fuelcost can be calculated as the product of the fuel consumption multipliedby the unit cost. The control unit can also calculate a unit cost ofelectric power generated by the generator from the calculated data ofgenerated electric power value, the data of generated electric energycalculated from the data, and the calculated data of fuel consumption. Auser can feel a glow of satisfaction at the ability of grasping the unitcost of electric power of the generator on the basis of the data ofhis/her usage pattern of the electric power generator set.

Preferably, the above-mentioned electric power generator set maycomprise means for externally transmitting the calculated result.Accordingly, data of electric powers can be transmitted to aninput/output means of the control unit of the electric power generatorset. If the input/output means is remote from the control unit, peopleat a place remote from the control unit can check the above-mentioneddata (data of the electric powers) so as to manage the electric powergenerator set in electric power. The user can collect the data by use ofthe data-registering mean so as to input the data to a device which isnot networked with the electric power generator set. The user at theplace of the operation-and-display device can also register theabove-mentioned data by use of the data-registering means so as to checkchange in the electric power supply and the electric energies.

If a system comprises a plurality of the above-mentioned power generatorsets connected in parallel to the external electric power supply, eachof the electric power generator sets preferably comprises means forcontrolling its own generator and inverter cooperatively, and means fordetecting current value from the external electric power supply, wherebythe inverters in all the electric power generator sets have abilities ofdetecting current value of the external electric power system.Therefore, only the electric power generator set requiring maintenanceis stopped so that the other electric power generator sets can be keptin interconnection with each other without stopping, and cumulativedrive times of the respective electric power generator sets can beequalized.

In the system comprising the plurality of electric power generator setsconnected in parallel, a control system of each electric power generatorset may preferably comprise means for communicating with the controlsystem of the other electric power generator set, and means for makingthe control system serve as a master unit for centralized control overthe other control system cooperatively. Therefore, only the electricpower generator set requiring maintenance is stopped so that the otherelectric power generator sets can be kept in interconnection with eachother without stopping.

In the system, the control system serving as the master unit maycomprise means for accumulating information of generated electric powerrequired of the other electric power generator set, the informationbeing transmitted from the control system of the other electric powergenerator set, calculating the load electric power of the system, anddetermining the number of the electric power generator sets to beoperated. Therefore, the equal output control and the control foroperating the specific electric power generator sets with the maximumoutput are enabled, and the accumulated operation times of therespective electric power generator sets are equalized.

In the system, the control system serving as the master unit maycomprise means for controlling the counted electric power generator setsto be operated so as to equalize outputs thereof. Accordingly, thespecific electric power generator sets are prevented from excessiveoperation and output, thereby prolonging a life of whole electric powersystem.

Alternatively, the control system serving as the master unit maycomprise means for controlling a specific one of the counted electricpower generators so as to maximize output thereof. Accordingly, thespecific electric power generator set is operated fully in output at thebest performance (operate in high efficiency). Furthermore, the electricpower generator sets to be rest may be selected from the electric powergenerator sets under operation.

The control system serving as the master unit may comprise means forrecognizing operation/pause state of its own electric power generatorset or the other electric power generator set and choosing the controlsystem serving as a next master unit. Accordingly, the inverter of theelectric power generator set to operate controls the other inverters asthe master unit for centralized control over generated outputs of itselfor the others.

The control system serving as the master unit may comprise means forshifting the electric power generator set to be operated at eachpredetermined period. Accordingly, operation times of the respectiveelectric power generator sets are equalized so as to prevent theaccumulative operation time of the specific electric power generator setfrom becoming longer than those of the other electric power generatorsets, thereby prolonging a life of the whole electric power system.

The control system serving as the master unit may comprise means forpreventing reverse electric power flow to the external electric powersupply by cooperating with the other control system. Therefore, themaster inverter controls output of itself or the other inverters,thereby preventing reverse electric power flow. A user can optionallyselect whether the reverse electric power flow is allowed or prevented.

Next, a modification of an electric power supply system which can supplyboth external electric power and generated electric power compriseswaste-heat recovery means for recovering waste heat from the engine soas to generate heat. The modified system may comprise means fordetecting information concerning heat energy consumed for generating hotwater, means for calculating heat energy, an amount of the heat energyand energy efficiency, means for registering the calculated result, andimage-displaying means for displaying the respective electric powers ofthe external electric power supply, the electric power generator set andload of the system, an amount of the heat energy and the energyefficiency in a table. Accordingly, various calculated data concerningthe electric power values and the water-heat energy can be displayed ascharts so that a user can get information concerning cost merit in noneed of complicated calculation.

The system may comprise means for calculating fuel consumption fordriving the engine, and image-displaying means for displaying respectiveelectric energies, the heat energy and the fuel consumption in a table.Accordingly, the unit cost of electric power generated by the generatorand the unit cost of the water-heat energy can be grasped more correctlyon the basis of the actual data, whereby a user can feel a glow ofsatisfaction at the ability of recognizing the effect of the system.

The system may comprise means for externally transmitting the calculatedresult. Accordingly, a user at a place distant from the generator canmonitor, analyze and register the generated electric energy by thegenerator and the amount of the recovered water-heat energy. Therefore,the system comprising the electric power generator set can be used moreeffectively, and so a user can feel a glow of satisfaction at theability of realizing the effect of his/her purchased system comprisingthe electric power generator sets.

Furthermore, the system may comprise means for communication such as toenable the system to be remotely operated. Accordingly, a user need notapproach the electric power generator set for changing operationpattern, whereby the cogeneration system can be used more comfortablyand effectively.

The system comprising the above-mentioned electric power generator setmay comprise means for detecting abnormality of the system based on thecalculated result and informing concerning the abnormality, therebyenabling quick action against failure of the system. It is advantageousin safety when the user of the system comprising the electric powergenerator set has little knowledge of machinery. It is also advantageousin minimizing reduction of energy cost merit caused by stop of thesystem comprising the electric power generator set.

The system comprising the electric power generator set may comprisemeans for minimizing ecological load or electric power cost based on thecalculated result. Therefore, a user can satisfactorily use the systemcomprising the electric power generator set in an optimal condition forits operation without complicated calculation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of an electric power generator set accordingto a first embodiment of the present invention.

FIG. 2 is a comparative table displayed by the electric power generatorset, representing hourly commercial electric energy and hourly generatedelectric energy.

FIG. 3 is a comparative table displayed by the electric power generatorset, representing monthly commercial electric energy and charge andmonthly generated electric energy and charge.

FIG. 4 is a comparative graph displayed by the electric power generatorset, representing the hourly commercial electric energy and the hourlygenerated electric energy.

FIG. 5 is a comparative graph displayed by the electric power generatorset, representing the monthly commercial electric energy and the monthlygenerated electric energy.

FIG. 6 is a conceptual diagram displayed by the electric power generatorset, representing the electric power systems with the supplied electricpower values corresponding to the respective electric power systems.

FIG. 7 is a conceptual diagram displayed by the electric power generatorset, representing the electric power systems with the monthly suppliedelectric energies corresponding to the respective electric powersystems.

FIG. 8 is a circuit diagram of an electric power generator set accordingto a second embodiment of the present invention.

FIG. 9 is a comparative table displayed by the electric power generatorset, representing the respective commercial, generated, and loadelectric energies, an amount of recovered water-heat energy, a virtualload electric power, and fuel consumption by the hour.

FIG. 10 is a comparative table displayed by the electric power generatorset, representing the respective commercial, generated and load electricenergies, the amount of recovered water-heat energy, the virtual loadelectric power, and fuel consumption by the month.

FIG. 11 is a graph displayed by the electric power generator set,representing the respective hourly commercial and generated electricenergies and the hourly amount of recovered water-heat energy.

FIG. 12 is a graph displayed by the electric power generator set,representing the respective monthly commercial and generated electricenergies and the monthly amount of recovered water-heat energy.

FIG. 13 is a system conceptual diagram displayed by the electric powergenerator set, representing the respective currently supplied electricenergies.

FIG. 14 is a system conceptual diagram displayed by the electric powergenerator set, representing the respective monthly electric energies.

FIG. 15 is a schematic diagram of an entire construction of an electricpower generation system according to a third embodiment of the presentinvention.

FIG. 16 is a diagram showing a construction of an electric powergenerator set of the electric power generation system.

FIG. 17 is a diagram showing a construction of an inverter of theelectric power generation system.

FIG. 18 is a diagram showing a wiring construction among a plurality ofinverters of the electric power generation system.

FIG. 19 is a flow chart for controlling the electric power generationsystem by use of the inverters and a control unit.

FIG. 20 is a flow chart continued from FIG. 19.

BEST MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the invention is explained on the basis ofattached drawings.

Explanation will be given on an electric power generator set 1 as anembodiment of the present invention according to FIG. 1. The presentinvention is applicable to any electric power generator set if it has aconverter and an inverter for converting output electric power of agenerator, not limited to the electric power generator set 1 of thepresent embodiment.

The electric power generator set 1 mainly comprises an engine 4 and agenerator 3. An output side of the generator 3 is provided withconverters 21 a and 21 b and inverters 6 a and 6 b, which convert outputelectric power of the generator 3.

A control system 2 for controlling these devices is provided in theelectric power generator set 1. The control system 2 has a control unit5 for controlling these devices and an operation-and-display unit 28 asmeans for input/output to the control unit 5.

In addition to the engine 4, the generator 3 and the inverters 6 a and 6b, the control unit 5 controls a radiator fan 7 a provided in a radiator7, a ventilating fan 15, a cooling water pump 16 and the like.

The engine 4 is an internal-combustion engine and disposed in amachinery room (not shown).

Liquid fuel, such as light oil, kerosene or heavy oil, or gaseous fuel,such as natural gas, town gas or sewage digestion gas, can be used asfuel for the engine 4, and the fuel is supplied to the engine 4 from anexternal fuel tank or an infrastructure (not shown) through a fuelsupply piping 49. A fuel flowmeter 50 is disposed in the fuel supplypiping 49 and detects data concerning fuel consumption of the engine 4so as to transmit the data to the control system 2. The data are takeninto account with a unit cost of fuel so as to compute a unit cost ofgenerated electric power in each time zone and an average unit cost ofthe generated electric power in a predetermined period. With regard tothe present embodiment, detection of flux is used as a method fordetecting fuel consumption. However, the method is not limited thereto.Detection of change of weight of a tank at the time of supplying fuel tothe tank or the like also is considerable as the method.

The radiator 7 of the engine 4 is disposed in a heat exchanger chamber(not shown). The ventilating fan 15 introduces outside air andventilates the machinery room and the heat exchanger chamber so as tocool air in the chambers.

A primary cooling water passage 8 is formed in the electric powergenerator set 1 so as to circulate cooling water of the engine 4 throughthe radiator 7. The radiator fan 7 a is provided in the radiator 7 anddrives so as to cool the cooling water passing through the radiator 7.

A starter 10 is disposed in the engine 4, and electric power is suppliedto the starter 10 from later-discussed load electric power lines U3 andV3 (including generated electric power lines U2 and V2) through atransformer 11. Otherwise, electric power may be supplied to the starter10 from a battery.

The generator 3 has a rotor (not shown), which has a field windingexcited by a direct-current electric power supply, on a rotation shaft12 connected to a drive shaft of the engine 4, and three-phase output istaken out by armatures disposed on a stator (not shown). The generator 3has armature windings 20 a and 20 b constituting the two-windingarmature for outputting the three-phase electric power. Either shuntwinding type or tandem type is suitable for arrangement of the armaturewindings 20 a and 20 b.

Electromagnetic induction is generated by rotation of theabove-mentioned field winding (rotor) so as to generate voltage on thearmature windings 20 a and 20 b respectively. Three output terminals areprovided on each of the armature windings 20 a and 20 b, wherebythree-phase electric power is outputted from the armature windings 20 aand 20 b.

The generator 3 is constructed to be revolving-field type such that thefield winding is disposed on the rotor, and the armatures on the stator.Alternatively, it may be revolving-armature type such that armatures aredisposed on a rotor, and a field winding on a stator, or that a rotor isdisposed on a permanent magnet, and armatures on a stator.

The generator 3 has an automatic voltage regulator (hereinafter,referred to as AVR) 14 so as to control supply electric power to theabove-mentioned field winding. The AVR 14 regulates the size of themagnetic field excited by the field winding so as to uniform the voltagevalue outputted from the armature windings 20 a and 20 b.

Each of the three-phase outputs 30 a and 30 b from the generator 3 isrectified and smoothed by each of the converters 21 a and 21 b whichconvert AC to DC, and after that, connected to direct-current inputparts of the inverters 6 a and 6 b. Then, the generated electric powerlines U2 and V2 as output lines from the inverters 6 a and 6 b areinterconnected with lines of a later-discussed external electric power(in this embodiment, commercial electric power supplied from an electricpower company or the like) system.

A commercial electric power system to be interconnected with theelectric power generator set 1 is not limited to that of a single-phasethree-wire type as shown in the embodiment of FIG. 1. Alternatively, athree-phase one-wire commercial electric power system may be used forinterconnection with the electric power generator set 1.

Lines U1, O1 and V1 of 200V single-phase three-wire type commercialelectric power system are drawn from a commercial electric power supply40 serving as an external electric power supply. The potentialdifference of 200V exists between the commercial electric power systemlines U1 and V1, and the commercial electric power system line O1 is aneutral line, whereby between the commercial electric power systems U1and O1 and between the commercial electric power systems O1 and V1 aregenerated the potential difference of 100V.

The commercial electric power system lines U1 and V1 are connected inparallel with the respective generated electric power system lines U2and V2 from the electric power generator set 1. The invertors 6 a and 6b also generates a potential difference of 200V between the generatedelectric power system lines U2 and V2, so as to correspond to thatbetween the commercial electric power systems U1 and V1, therebyensuring the interconnection for supplying electric power from thecommercial electric power system lines U1, V1 to the generated electricpower system lines U2 and V2.

Load electric power interconnected as the above (load electric powersystem lines U3, O3 and V3) is supplied to electric power-consuminginstruments (hereinafter, referred to as single-phase loads) 24.

Current transformers CT1 and CT2 are provided on the respectivecommercial electric power system lines U1 and V1 so that the inverter 6a detects current value of the commercial electric power supplied to thesingle-phase load 24 through the commercial electric power system linesU1 and V1.

The current value of the commercial electric power system lines U1 andV1 is changed corresponding to electric power consumption of thesingle-phase loads 24. Therefore, the invertors 6 a and 6 b uniform thegenerated electric power (load electric power) so as to stably supplythe load electric power to the single-phase loads 24.

In this way, the generated electric power system lines U2 and V2 aresupplied with suitable generated electric power from the inverters 6 aand 6 b in correspondence to the current value of the commercialelectric power system lines U1 and V1 detected by the currenttransformers CT1 and CT2.

A plurality of (two in the present embodiment) inverters 6 a and 6 b arenetworked with each other by multidrop. The inverter 6 a calculates arequired set output (electric power) value on the basis of the detectedcurrent value of the commercial electric power system lines U1 and V1.Then, the inverter 6 a transmits the set output value to the otherinverter 6 b. The inverter 6 b controls output so as to adjust it to thetransmitted set output value.

Hereafter, explanation will be given on an example of actuation of theelectric power generator set 1 by the above-mentioned interconnection.

(1) When Electric Power Consumption of the Single-Phase Loads Increases:

As demand electric power of the load electric power system lines U3, O3and V3 increases, the commercial electric power flowing in thecommercial electric power system lines U1, O1 and V1 increases. The“load electric power system lines” mean the commercial electric powersystem lines interconnected with the generated electric power systemlines.

Increment of the commercial electric power in the commercial electricpower system lines U1 and V1 is calculated as a product of increment ofthe current value detected by the current transformers CT1 and CT2multiplied by the detected voltage in the output part of the inverter 6a. Corresponding to this, the inverter 6 a controls itself so as toincrease the generated electric power to the generated electric powersystem lines U2 and V2, and controls the inverter 6 b.

(2) When Electric Power Consumption of the Single-Phase Loads Decreases:

As the demand electric power of the load electric power system lines U3,O3 and V3 decreases, the commercial electric power flowing in thecommercial electric power system lines U1, O1 and V1 decreases.

Decrement of the commercial electric power in the commercial electricpower system lines U1 and V1 is calculated as a product of increment ofthe current value detected by the current transformers CT1 and CT2multiplied by the detected voltage in the output part of the inverter 6a. Corresponding to this, the inverter 6 a controls itself so as todecrease the generated electric power to the generated electric powersystem lines U2 and V2, and controls the inverter 6 b.

Explanation will now be given on a electric power control system usingthe control system 2.

In addition to serving as a control mechanism of the electric powergenerator set 1, the control system 2 functions as a electric powercontrol system for controlling electric power, such as the generatedelectric power and the load electric power.

The control unit 5 of the control system 2 controls drive of devicesconstituting the electric power generator set 1, and calculates andstores electric power value and value of electric energy of eachelectric power system. The control unit 5 has a memory as a storagemeans, and a computing unit (CPU) as a calculation means.

Data concerning electric power directly detected for the electric powergenerator set 1 include a current value of the commercial electricpower, and a current value and a voltage value of the generated electricpower.

As mentioned above, the inverter 6 a can detect the current value of thecommercial electric power through the current transformers CT1 and CT2.The inverter 6 transmits the detected data concerning the commercialelectric power to the control unit 5, and the control unit 5 stores thedata.

The inverters 6 a and 6 b use respective circuits therein to detect thecurrent value and voltage value of the generated electric powerconverted and outputted by the inverters 6 a and 6 b. Then, the detecteddata concerning the generated electric power are also transmitted to andstored by the control unit 5.

Next, explanation will be given on data calculated based on the detecteddata.

The commercial electric power of the commercial electric power systemlines U1 and V1 and the generated electric power of the generatedelectric power system lines U2 and V2 are combined into the loadelectric power of the load electric power system lines U3 and V3. Thecomputing unit in the control unit 5 calculates a value of the loadelectric power on the basis of the detected data concerning thecommercial electric power and the generated electric power.

The control unit 5 stores the calculated data concerning the loadelectric power value.

The control unit 5 calculates each electric energy by detection andcalculation of the data concerning each electric power. Each electricenergy is obtained by time integration of the corresponding electricpower. In the present embodiment, the control unit 5 calculates electricenergies supplied to the loads every a fixed time (one hour, in thepresent embodiment).

In this way, the control unit 5 calculates a commercial electric energyand a generated electric energy on the basis of the calculated valuesconcerning the commercial electric power and the generated electricpower, respectively, and a load electric energy is calculated on thebasis of the calculated value of the load electric power.

The control unit 5 stores these calculated data concerning therespective electric energies.

Summarizing the above, the data concerning the commercial electric powervalue and the generated electric power value detected by the inverter 6a are transmitted to and stored by the control unit 5. In the presentembodiment, the data concerning the commercial electric power value isrepresented by the data of the detected current value of the commercialelectric power, and the data concerning the generated electric powervalue is represented by the data of the detected current value andvoltage value of the generated electric power.

The control unit 5 calculates data of the respective electric powervalues and data of the respective electric energies, and also storagesthem. In the present embodiment, the data of the electric power valuesare data of the commercial electric power value, generated electricpower value and load electric power value. The data of the respectiveelectric energies are data of the commercial electric energy, generatedelectric energy and load electric energy.

As mentioned above, the electric power generator set 1 can beinterconnected with the external electric power supply (commercialelectric power supply) by the inverters 6 a and 6 b, and the electricpower generator set 1 comprises: means for detecting informationconcerning respective electric powers of the external electric powersupply and the electric power generator set 1; means for calculating therespective electric powers and electric energies of the externalelectric power supply, the electric power generator set and the loads;and means for storing the calculated electric powers and electricenergies.

The information concerning the respective electric powers of theexternal electric power supply (commercial electric power supply 40) andthe electric power generator set 1 is data concerning their currentvalues and voltage value, and the means for detecting this informationcomprises the inverters 6 a and 6 b.

The means for storing each electric power and energy comprises thecontrol unit 5.

Accordingly, the entire electric power generator set can be miniaturizedcompared with a electric power generator set constituted by attaching aninverter for interconnection to an existing generator unit mainlycomprising the engine 4 and the generator 3.

The electric power control system comprising the inverters 6 a and 6 bfor interconnection and the control unit 5 are integrated into theelectric power generator set 1 so that there is no necessity of adding anew device, whereby cost is reduced and an additional space forproviding the additional device is not required.

The operation-and-display unit 28 serving as an element of the electricpower generator set 1 is input/output means, which serves as not onlyinput means for transmitting commands to the control unit 5 but alsooutput means for receiving data transmitted from the control unit 5.

The control unit 5 is provided with an output terminal for transmittingdata, and as shown in FIG. 1, the operation-and-display unit 28 servingas the input/output means is networked to the control unit 5 through asignal wire system. Alternatively, the operation-and-display unit 28 maybe constructed as a remote control board in radio communication with thecontrol unit 5.

Instead of the operation-and-display unit 28 or in addition thereto, awidely used general-purpose personal computer 35 can be used asinput/output means.

The electric power generator set 1 and a remote monitoring system(central remote monitoring center) remotely provided from the electricpower generator set 1 comprise respective communication adapters 31 soas to connect the control unit 5 of the electric power generator set 1to an supervisory operation-and-display unit 29 of the remote monitoringsystem. The adapters 31 enable two-way communication between the controlunit 5 and the supervisory operation-and-display unit 29, that is,between an installation place of the electric power generator set 1 anda remote place therefrom.

On the contrary to the operation-and-display unit 28 provided within theelectric power generator set 1, the supervisory operation-and-displayunit 29 is an example as an operation-and-display device disposedoutside the electric power generator set 1.

The communication means between the control unit 5 and the supervisoryoperation-and-display unit 29 is not limited to radio communication, andit may be wired communication using a communication line such as atelephone line.

Accordingly, due to the electric power generator set 1 having theoperation-and-display unit 28 and the means for external transmittingthe calculated results (the output terminal, the communication adapters31 and the like), the data concerning electric powers, such as the abovedetected data and calculated data, stored in the control unit 5 of theelectric power generator set 1 can be checked and managed at a placeremote from the electric power generator set 1.

In the present embodiment, the centralized control unit 5 can transmitdata to both the operation-and-display devices 28 and 29. Alternatively,the centralized control unit 5 may be able to transmit data to only oneof them.

The electric power generator set 1 has image-displaying means fordisplaying graphs of the respective electric energies, i.e., a display32 provided in the operation-and-display unit 28. Explanation will begiven on charts displayed on the display 32 as follows with reference toFIGS. 2 to 7, which may be applied to the supervisoryoperation-and-display unit 29 (or the personal computer 35).

The operation-and-display unit 28 serving as the input/output means hasthe display 32 for displaying diagrams of data, which are diagrammatizedby a processing program stored in the operation-and-display unit 28.

In the present embodiment, the current transformers CT1 and CT2 detectthe current of the commercial electric power from the commercialelectric power supply 40, and circuits in the inverters 6 a and 6 bdetect the current and voltage of the generated electric power from thegenerator 3. However, means for detection thereof are not limited to theabove.

The control unit 5 processes the detected data concerning the commercialelectric power and the generated electric power so as to calculate dataconcerning electric power value and electric energy for the loads.However, means for calculation thereof is not limited to the controlunit 5. For example, the operation-and-display unit 28 serving as theinput/output means may receive the detected data and calculate by use ofa computer and processing program stored therein.

Firstly, a comparative table about the hourly commercial and generatedelectric energies shown in FIG. 2 will be described.

According to the above-mentioned processing program, the display 32displays a table in which the calculated commercial electric energy,generated electric energy and load electric energy every hour are linedup by the hour. In the present embodiment, as mentioned above, sinceeach of the electric energies is calculated every hour, each of thecalculated electric energies is listed hour by hour in the list.

Currently, each of the electric energies means the electric energy ofeach of the external electric power supply, the electric power generatorset and the loads. The display 32 serves as the image-displaying means.

Accordingly, a user of the electric power generator set 1 can feel aglow of satisfaction at its ability of monitoring the electric energygenerated by the generator 3 and realizing the effect of his/herpurchased electric power generator set 1.

Next, a comparative table about the monthly commercial and generatedelectric energies and electric charges shown in FIG. 3 will bedescribed.

According to the above-mentioned processing program, the above-mentionedcalculated data, i.e., the hourly commercial electric energy, generatedelectric energy and load electric energy can be totaled at each monthlyperiod so as to calculate respective monthly electric energies, and thedisplay 32 can display a list of the monthly electric energies andcorresponding electric charges.

The operation-and-display unit 28 previously memorizes a unit cost ofthe commercial electric power per kWh (purchased electric power cost)shown in FIG. 3 informed by the commercial energy supplier (electricpower company). The control unit 5 calculates a unit cost of thegenerated electric power per kWh on the basis of the cost of fuelrequired for driving the engine 4, and corresponding toincrease/decrease of fuel consumption.

The unit cost per kWh and charge of the generated energy means a runningcost of the electric power generator set 1.

According to the above construction, a user can compare the commercialelectric energy with the generated electric energy every month.Furthermore, the user can also compare the charge of the commercialelectric power with that of the generated electric power. Therefore, theuser can compare the running cost of the generated electric power withthe purchase cost of the commercial electric power so as to confirm arunning merit of the electric power generator set 1.

The case of comparison every month is shown in the embodiment in FIG. 3.Alternatively, the comparison may be done every day or every year.

Further, the operation-and-display unit 28 can calculate how long timeis required to recover the capital spending of the electric powergenerator set 1 on the basis of the running merit of the electric powergenerator set 1 (the purchasing electric power cost minus the runningcost) so that the user can monitor it.

With regard to the above construction, the electric power generator setcomprises calculation means for calculating fuel consumption of theengine and image-displaying means for displaying each of the electricenergies and the fuel consumption in a table.

Currently, each of the electric energies means electric energy of eachof the external electric power supply, the electric power generator setand the loads. The control unit 5 serves as the calculation means is thecontrol unit 5, and the display 32 serves as the image-displaying means.

Accordingly, the fuel flowmeter 50 detects data concerning the fuelconsumption of the engine 4 and transmits the data to the control unit 5of the electric power generator set 1, and the control unit 5 cancalculate a fuel cost (¥/month or ¥/hour), i.e., a product of the datamultiplied by the known unit cost of fuel (¥/m³ or ¥/litter) which hasbeen already inputted into the control unit 5.

The control unit 5 can also calculate a unit cost of the electric powergenerated by the generator 3 from the calculated data of the generatedelectric power value, the data of the generated electric energycalculated from the data generated electric power value, and thecalculated data of fuel consumption. A user can feel a glow ofsatisfaction at the ability of grasping the unit cost of the electricpower of the generator 3 on the basis of the actual data representinghis/her working conditions of the electric power generator set.

A graph of FIG. 4 representing hourly comparison of the commercial andgenerated electric energies will now be described.

The graph of FIG. 4 is made by graphing the comparative table in FIG. 2.The axis of abscissas designates hour-by-hour passage of time, and theaxis of ordinates designates variations of the respective electricenergies.

Due to the above construction, a user can compare the electric energiessupplied by the respective electric power systems with each other everyhour, so as to know in which hour the load electric power increases ordecreases in a day, and to know what is the best electric powergenerating pattern for cost reduction corresponding to items of his/hercontract with the electric power company. Therefore, the user canrecognize the effect of his/her investment for equipment of the electricpower generator set 1.

A graph of FIG. 5 representing comparison of the monthly commercial andgenerated electric energies will be described.

The graph of FIG. 5 represents the monthly comparison of the commercialand generated electric energies and variation of the load electricenergy. The axis of abscissas designates month-by-month passage of time,and the axis of ordinates designates variation of the respectiveelectric energies.

According to the above construction, a user can compare the electricenergies supplied by the respective electric power systems with eachother every month, so as to know in which month the load electric powerincreases or decreases in a year, and to know what is the best electricpower generating pattern for cost reduction corresponding to items ofhis/her contract with the electric power company. Therefore, The usercan recognize the effect of his/her investment for equipment of theelectric power generator set 1.

A conceptual diagram of electric power system shown in FIG. 6representing electric power values currently supplied by the respectiveelectric power systems will be described.

According to the above-mentioned processing program, the display 32displays the conceptual diagram of the electric power systems, on whichelectric power values supplied by the respective electric power systemscan be displayed corresponding to the respective electric power systems.The electric power values and fuel consumption displayed on the display32 are the above-mentioned detected data and calculated data, andupdated at each period of detection of the commercial current value,generated current value and generated electric power value by theinverter 6 a. Namely, change of each electric power value is displayedon the display 32 in real time.

According to the above construction, a user can feel a glow ofsatisfaction at the ability of checking momentarily change of theelectric powers supplied by the respective electric power systems, andat the ability of easily grasping variation of the supplied electricpowers in image because the supplied electric power values are displayedcorresponding to the conceptual diagram.

A conceptual diagram of electric power system shown in FIG. 7representing electric energies monthly supplied by the respectiveelectric power systems will be described.

According to the above-mentioned processing program, the display 32displays the conceptual diagram of the electric power systems, on whichthe monthly electric energies supplied by the respective electric powersystems and the monthly fuel consumption can be displayed correspondingto the respective electric power systems. Each of the monthly electricenergies is the monthly total of the calculated data of thecorresponding hourly electric energies, similarly to the comparativetable of FIG. 3 representing the monthly electric energies and chargesof the respective commercial and generated electric powers.

Due to the above construction, a user can feel a glow of satisfaction atthe ability of checking the monthly electric energies supplied by therespective electric power systems, and at the ability of easily graspingcomparison of the monthly electric energies in image because thesupplied electric energies are displayed corresponding to the conceptualdiagram.

The period of the comparison is not limited to each month, and it may beeach day or each year.

The operation-and-display unit 28 serving as the input/output means ofthe control unit 5 can be used as output means for taking out each ofthe above-mentioned data from the electric power generator set 1.

In this regard, the operation-and-display unit 28 has a mechanism foroutputting to an IC card (card-like device) 33 serving as data-storagemeans, and a mechanism for outputting to a printer 34 serving asdata-registering means. Therefore, each of the above-mentioned data canbe memorized in the IC card 33, and numerical information of each of theabove-mentioned data and the above-mentioned diagrams (such as FIGS. 2to 7) can be printed by the printer 34.

Due to the above construction, each of the above-mentioned data can becollected by the IC card 33 so as to be read by a device which is notnetworked with the electric power generator set 1. Especially if acomputer reads the data from the IC card 33 and the computer stores adata processing program different from those stored in the control unit5 and operation-and-display unit 28, the data processing can enhancevariation of electric power management.

The printer 34 can print the numerical information of each of theabove-mentioned data and the above-mentioned diagrams. Namely, due toeach of the above-mentioned data registered by the data-registeringmeans, the user can check change of electric power supply and electricenergy at the place of the operation-and-display unit 28. Especially inthe case of providing the printer 34, the printer 34 can serve as mainmeans for checking the data and diagrams thereof, whereby a small liquidcrystal display, for example, can be used as the display 32 so as toreduce costs thereof.

Next, a cogeneration system as a second embodiment of the electric powersupply system concerning the present invention will be described inaccordance with FIG. 8.

A electric power generator set 1′ of the second embodiment mainlycomprises an engine 4 and a generator 3, and also comprises a controlsystem 2 for controlling these devices. The control system 2 has acontrol unit 5 for controlling these devices and anoperation-and-display unit 28 as means for input/output to the controlunit 5. The electric power generator set 1′ has a water-heat energyrecovery mechanism.

The electric power generator set 1′ of the second embodiment has thesame engine 4 and generator 3 and the same interconnection with acommercial electric power supply 40 serving as an external electricpower supply via inverters 6 a and 6 b as those of the electric powergenerator set 1 of the first embodiment.

Explanation will be given on the water-heat energy recovery mechanism ofthe electric power generator set 1′. The water-heat energy recoverymechanism is the general term representing a primary cooling waterpassage 8, a cooling water pump 16, a heat exchanger 41, a secondarycooling water passage 42, an entrance side thermometer 44, an exit sidethermometer 45, a flowmeter 46, a hot water storage tank 47 and so on.

The energy recovery mechanism and a generation unit of the electricpower generator set 1′ constitute the cogeneration system serving as thesystem using a generator according to the present invention. With regardto this system, the energy recovery mechanism functions as means forrecovering waste heat of the electric power generator set.

The electric power generator set 1′ comprises the primary cooling waterpassage 8 in which primary cooling water is circulated through the heatexchanged 41 and the radiator 7 by the cooling water pump 16. Theradiator 7 comprises a radiator fan 7 a, which drives to cool theprimary cooling water circulating in the radiator 7.

The secondary cooling water passage 42 is provided in the heat exchanger41, and heat energy of the primary cooling water is conducted tosecondary cooling water by heat conduction. A circulating pump (notshown) circulates the secondary cooling water in the secondary coolingwater passage 42. A part of the secondary cooling water is drawn intothe hot water storage tank 47 and contacts water stored in the hot waterstorage tank 47 so that heat energy of the secondary cooling water isconducted to the water in the hot water storage tank 47 by heatconduction. Accordingly, waste heat of the engine 4 raises thetemperature of the water in the hot water storage tank 47 so as to makethe water into hot water, whereby the heat is recovered as water-heatenergy.

The entrance side thermometer 44 and the exit side thermometer 45 aredisposed at entrance side and exit side of the hot water storage tank inthe secondary cooling water passage 42 respectively and the flowmeter 46is disposed at the entrance side or the exit side of the secondarycooling water passage 42 so as to quantitatively grasp how much wasteheat generated in the engine 4 is recovered.

In the present embodiment, the energy of waste heat of the engine 4 isrecovered for the energy of hot water in the hot water storage tank 47through the primary cooling water and the secondary cooling water.Alternatively, the primary cooling water passage 8 may be directlypassed through the hot water storage tank 47 so as to recover heat fromthe primary cooling water to the hot water storage tank 47.

Cooling of the primary cooling water by the radiator 7 and the radiatorfan 7 a is essentially unnecessary for maximizing the energy efficiencybecause the cooling means waste of the heat of the engine 4 from theelectric power generator set 1′. However, in use of the generator, whendemand (used amount) of the water-heat energy is extremely less thandemand of electric energy (the load electric energy), waste heat of theengine 4 cannot be recovered completely and the temperature of theprimary cooling water is raised so that the engine 4 may be troubled.The radiator 7 and the radiator fan 7 a are provided for safetysupposing such a situation.

Explanation will now be given on a electric power control system usingthe control system 2.

In addition to serving as the mechanism for controlling the electricpower generator set 1, the control system 2 functions as a electricpower control system which controls electric power, such as thegenerated electric power and the load electric power, and the water-heatenergy obtained by recovering waste heat generated from the engine 4.

The control unit 5 of the control system 2 controls drive of each deviceconstituting the electric power generator set 1′, and can calculate andstore electric power value (kW) and electric energy value (kWh) of eachelectric power system, the water-heat energy (kW) and the amount ofrecovered water-heat energy (kWh). The control unit 5 has a memory asstorage means and a computer (CPU) as calculation means.

The electric power generator set 1′ has two directly detected valuesconcerning electric powers, i.e., a current value of the commercialelectric power and a current value of the generated electric power.

As mentioned above, the inverter 6 a can detect the current value of thecommercial electric power (A) via the current transformers CT1 and CT2.The inverter 6 a transmits the detected data concerning the commercialelectric power to the control unit 5, and the control unit 5 stores thedata.

The inverters 6 a and 6 b use their circuits for detecting the currentvalue of the generated electric power (A), which is converted andoutputted by the inverters 6 a and 6 b. The detected data concerning thegenerated electric power are also transmitted to and stored by thecontrol unit 5.

The electric power generator set 1′ has three directly detected valuesconcerning water-heat energy, i.e., an entrance side temperature and anexit side temperature of the secondary cooling water in the heat waterstorage tank, and a flux in the secondary cooling water passage. Namely,the entrance side thermometer 44 and the exit side thermometer 45 aredisposed at entrance side and exit side of the hot water storage tank inthe secondary cooling water passage 42 respectively so as to detect anentrance side temperature T1 (° C.) and an exit side temperature T2 (°C.) of the secondary cooling water. The flowmeter 46 is disposed at theentrance side or the exit side of the secondary cooling water passage 42so as to detect a flux L (litter/second) of the secondary cooling water.The detected data are transmitted to and stored in the control unit 5.The flowmeter 46 may be omitted due to the characteristic of thecirculating pump (not shown), or provided for inputting of flux.

Next, explanation will be given on data concerning electric powercalculated from the above-mentioned detected data.

The commercial electric power of the commercial electric power systemlines U1 and V1 and the generated electric power of the generatedelectric power system lines U2 and V2 are combined into the loadelectric power of the load electric power system lines U3 and V3. Thecontrol unit 5 calculates a value of the load electric power on thebasis of the detected data concerning the commercial electric power andthe generated electric power by its computer.

The control unit 5 stores the calculated data concerning the loadelectric power value.

The control unit 5 calculates each electric energy by detection andcalculation of the data concerning each electric power. Electric energy(kWh) is obtained by time integration of electric power (kW). In thepresent embodiment, the control unit 5 calculates the electric energysupplied to loads for an established time (an hour in the presentembodiment) at each of the established periods.

Then, the control unit 5 calculates commercial electric energy and thegenerated electric energy on the basis of calculated commercial electricpower value and generated electric power value, thereby calculating loadelectric energy on the basis of the calculated load electric powervalue.

The control unit 5 stores the calculated data concerning the electricenergy.

Next, explanation will be given on data concerning the water-heat energycalculated from the above-mentioned detected data.

The detected data, i.e., the entrance side temperature T1 (° C.), theexit side temperature T2 (° C.) and the flux L (litter/second) of thesecondary cooling water, are processed with a constant, i.e., specificheat of water K (kJ/litter*° C.), according to a formula K*(T1−T2)*L soas to calculate an energy per unit time (kW=kJ/second) of hot waterrecovered into the hot water storage tank 47. An amount of recoveredwater-heat energy (kWh) is obtained by time integration of thewater-heat energy per unit time (kW).

Summarizing the above, the control unit 5 receives and stores datadetected by the inverter 6 a concerning the commercial electric powervalue and generated electric power value. The control unit 5 calculatesthe load electric power value, commercial electric energy, the generatedelectric energy and load electric energy from the above-mentioneddetected data, and stores the calculated data.

Also, the control unit 5 receives and stores data detected by theentrance side thermometer 44, the exit side thermometer 45 and theflowmeter 46 concerning the water-heat energy. The control unit 5calculates the water-heat energy and the amount of recovered water-heatenergy from the above-mentioned detected data, and stores the calculateddata.

Further, it is possible that the control unit 5 having known the unitcost of fuel (¥/m³ or ▮/litter) receives data detected by the fuelflowmeter 50 concerning fuel consumption of the engine 4 and calculatesa fuel cost (¥/month or ¥/hour) as the product of the detected datamultiplied by the unit cost.

As mentioned above, the system using the electric power generator set 1′comprises: means for detecting data concerning heat energy spent forproducing hot water; means for calculating the heat energy, the amountof the heat energy and the efficiency of the energy; and means forstoring the calculated results.

Currently, the system using the electric power generator set 1′ meansthe cogeneration system. The entrance side thermometer 44, exit sidethermometer 45 and flowmeter 46 serve as the means for detecting dataconcerning heat energy spent for producing hot water. The control unit 5serves as the means for calculating the heat energy, the amount of theheat energy and the efficiency of the energy, and the means for storingthe calculated results.

Compared with a cogeneration system constituted by attaching a heatrecovery system and a control system to an existing generator unitmainly comprising the engine 4 and the generator 3, the whole electricpower generator set 1′ can be appropriately reduced in size (and space).

The electric power generator set 1′ integrally comprises the inverters 6a and 6 b for interconnection and the water-heat energy recoverymechanism, and comprises the control unit 5 for collectively controllingeach device of the electric power generator set 1′, thereby requiring noadditional device for controlling electric power and heat energythereof, and saving costs and a space for such an additional device.

The operation-and-display unit 28 serving as an element of the electricpower generator set 1′ is input/output means, which serves as not onlyinput means for transmitting commands to the control unit 5 but alsooutput means for receiving data transmitted from the control unit 5.

The control unit 5 is provided with an output terminal for datacommunication, and as shown in FIG. 1, the operation-and-display unit 28serving as the input/output means is networked to the control unit 5through a signal wire system. Alternatively, the operation-and-displayunit 28 may be a remote control board in radio communication with thecontrol unit 5.

Instead of the operation-and-display unit 28 or in addition thereto, awidely used general-purpose personal computer 35 may be used as theinput/output means.

The electric power generator set 1 and a remote monitoring system(central remote monitoring center) remotely provided from the electricpower generator set 1′ comprise respective communication adapters 31 soas to connect the control unit 5 of the electric power generator set 1to an supervisory operation-and-display unit 29 of the remote monitoringsystem. The adapters 31 enable two-way communication between the controlunit 5 and the supervisory operation-and-display unit 29, that is,between an installation place of the electric power generator set 1 anda remote place therefrom.

On the contrary to the operation-and-display unit 28 provided within theelectric power generator set 1′ , the supervisory operation-and-displayunit 29 is an example as an operation-and-display device disposedoutside the electric power generator set 1′.

The communication means between the control unit 5 and the supervisoryoperation-and-display unit 29 is not limited to radio communication, andit may be wired communication using a communication line such as atelephone line.

In the present embodiment, the centralized control unit 5 can transmitdata to both the operation-and-display devices 28 and 29. Alternatively,the centralized control unit 5 may be able to transmit data to only oneof them.

Accordingly, due to the electric power generator set 1′ having theoperation-and-display unit 28 and the means for external transmittingthe calculated results (the output terminal, the communication adapters31 and the like), the data concerning electric powers, such as the abovedetected data and calculated data, stored in the control unit 5 of theelectric power generator set 1′ can be checked and managed in analysis,registering and so on of the data by use of the operation-and-displayunit 28 of the electric power generator set 1′ or a device remote fromthe electric power generator set 1′ (such as the personal computer 35 orthe supervisory operation-and-display unit 29). Furthermore, on thebasis of the above data and corresponding to change of the drivingcondition of the electric power generator set 1′, inputting operationcan be done with the operation-and-display unit 28, or with thesupervisory operation-and-display unit 29 in no need of a user'sapproach to the electric power generator set 1′, thereby increasingfacilitation for using the cogeneration system. Accordingly, a user cansatisfactorily realize the effect of his/her purchased cogenerationsystem.

Explanation will be given on charts displayed on a display 32 providedin the operation-and-display unit 28 as follows with reference to FIGS.9 to 14, which is also applicable to the supervisoryoperation-and-display unit 29 (or the personal computer 35).

The operation-and-display unit 28 serving as the input/output means hasthe display 32, which displays the data diagrammatized according to aprocessing program stored in the operation-and-display unit 28.

In the present embodiment, the current transformers CT′1 and CT′2 detectthe current of the commercial electric power from the commercialelectric power supply 40, and circuits in the inverters 6 a and 6 bdetect the current of the generated electric power from the generator 3.However, means for detection thereof are not limited to the above.

The control unit 5 processes the detected data concerning the electricpower values and water-heat energy so as to calculate data concerningthe electric power values, the water-heat energy, the electric energiesand the amount of recovered water-heat energy. However, means forcalculation thereof is not limited to the control unit 5. For example,the operation-and-display unit 28 serving as the input/output means mayreceive the detected data and calculate by use of a computer andprocessing program stored therein.

Firstly, explanation will be given on a comparative table of FIG. 9, inwhich the commercial, generated and load electric energies, the amountof recovered water-heat energy, a virtual load electric energy and fuelconsumption are listed by the hour.

According to the above-mentioned processing program, the display 32displays a table in which the above calculated date, i.e., thecommercial electric energy, the generated electric energy, the loadelectric energy, the amount of recovered water-heat energy, the virtualload electric energy and the fuel consumption are lined up by the hour.As mentioned above, since each of the electric energies is calculatedevery hour, each of the calculated electric energies is listed hour byhour in the list.

If the generator of the present invention is not used, the commercialelectric power must essentially cover all the electric power requiredfor electric power consumption devices (including a device forgenerating hot water). The “virtual” load electric energy required inthis case is defined as the total of the commercial electric energy, thegenerated electric energy and the amount of recovered water-heat energy.

Due to the above construction, a user of the electric power generatorset 1′ can satisfactorily monitor electric energy generated by thegenerator 3 and realize the effect of his/her purchased electric powergenerator set 1′.

Next, explanation will be given on a comparative table of FIG. 10, inwhich the commercial, generated and load electric energies, the amountof recovered water-heat energy, the virtual load electric energy and thefuel consumption are listed monthly.

According to the above-mentioned processing program, the hourlycalculated data of the commercial electric energy, the generatedelectric energy, the load electric energy, the amount of recoveredwater-heat energy, the virtual load electric energy and the fuelconsumption are totaled at each monthly period so as to calculate therespective monthly electric energies and the monthly amount of heatenergy, and the display 32 can display a list of the monthly electricenergies and corresponding electric charges.

The operation-and-display unit 28 previously memorizes a unit cost ofthe commercial electric power per kWh (purchased electric power cost)shown in FIG. 10 informed by the commercial energy supplier (electricpower company). The control unit 5 calculates a unit cost of thegenerated electric power per kWh on the basis of the cost of fuelrequired for driving the engine 4, and corresponding toincrease/decrease of fuel consumption.

A user can compare monthly variation of the virtual load electric power(Y/month) with the total monthly charge of the commercial electricpower, the generated electric power and the water-heat energy, as shownin FIG. 10, so as to easily grasp the effect of his/her installation ofcogeneration system of the present invention, i.e., the amount ofreduction of energy cost. Further, if data of overhead expensesconcerning the generator of the present invention, such as its purchase,appurtenant construction, management and maintenance, repair, andpersonnel expenses are taken into account in calculation of unit costs(per kWh) and monthly charges of the generated electric power and thewater-heat energy, a user can further accurately predict a periodrequired for recovery of investment for equipment of the electric powergenerator set, thereby increasing his/her satisfactory appreciation. Theunit cost (per kWh) of the generated electric power and the water-heatenergy are calculated by the following formula:

(Unit cost per kWh of the generated electric power and the water-heatenergy (¥/kWh))=(Fuel cost(¥/month))/(Total of the monthly usedgenerated electric power and water-heat energy (kWh/month))

The comparison is monthly in the embodiment of FIG. 10. Alternatively,the comparison may be daily or yearly.

An example of graphs, shown in FIG. 11, representing the hourlycommercial and generated electric energies and the hourly amount ofrecovered water-heat energy will be described.

The graph of FIG. 11 is made by graphing the comparative table in FIG.9. The axis of abscissas designates hour-by-hour passage of time, andthe axis of ordinates designates variations of the respective electricenergies.

Due to the above construction, a user can compare the electric energiessupplied by the respective electric power systems with each other everyhour, so as to know in which hour the load electric power increases ordecreases in a day, and to know what is the best electric powergenerating pattern for cost reduction corresponding to items of his/hercontract with the electric power company. Therefore, the user canrecognize the effect of his/her investment for equipment of the electricpower generator set 1′.

An example of graphs, shown in FIG. 12, representing the monthlycommercial and generated electric energies and the monthly amount ofrecovered water-heat energy will be described.

The graph in FIG. 12 represents comparison of the monthly commercialelectric energy with the monthly generated electric energy, and showsvariation of the monthly load electric energy. The axis of abscissasdesignates month-by-month passage of time, and the axis of ordinatesdesignates variations of the respective electric energies.

Due to the above construction, a user can compare the electric energiessupplied by the respective electric power systems with each other everymonth, so as to know in which month the load electric power increases ordecreases in a year, and to know what is the best electric powergenerating pattern for cost reduction corresponding to items of his/hercontract with the electric power company. Therefore, The user canrecognize the effect of his/her investment for equipment of the electricpower generator set 1′.

An example of conceptual diagrams of electric power system, shown inFIG. 13, representing electric power values currently supplied by therespective electric power systems will be described.

According to the above-mentioned processing program, the display 32displays the conceptual diagram of the electric power systems, on whichelectric power values supplied by the respective electric power systemscan be displayed corresponding to the respective electric power systems.The electric power values, the water-heat energy and the fuelconsumption displayed on the display 32 are the above-mentioned detecteddata and calculated data, and updated at each period of detection of thecommercial and generated current values by the inverter 6 a. Namely,change of each electric power value is displayed on the display 32 inreal time.

Incidentally, the “generated energy” in FIG. 13 is magnitude of usableenergy (i.e., the electric energy and the recovered water-heat energy)out of various energies generated by the generator. This is counted asan important parameter together with the weight of used fuel per unittime and the combustion energy of fuel per unit weight thereof tounderstand the energy efficiency of the generator (=(the generatedenergy)/(the combustion energy of fuel)*100(%)).

Due to the above construction, a user can satisfactorily checkmomentarily change of the electric powers supplied by the respectiveelectric power systems, and satisfactorily easily grasp variation of thesupplied electric powers in image because the supplied electric powervalues are displayed corresponding to the conceptual diagram.

An example of conceptual diagrams of electric power system, shown inFIG. 14 representing monthly supplied electric energies supplied therespective electric power systems and the monthly amount of heat energywill be described.

According to the above-mentioned processing program, the display 32displays the conceptual diagram of the electric power systems, on whichthe monthly supplied electric energies of the respective electric powersystems, the monthly amount of recovered water-heat energy, and themonthly fuel consumption can be displayed corresponding to therespective electric power systems. Each of the monthly electric energiesis the monthly total of the calculated data of the corresponding hourlyelectric energies and the hourly amount of recovered water-heat energy,similarly to the comparative table of FIG. 10 representing therespective monthly commercial and generated electric energies, themonthly amount of recovered water-heat energy and the monthly virtualload electric energy.

Due to the above construction, a user can satisfactorily check themonthly electric energies supplied by the respective electric powersystems, and satisfactorily easily grasp comparison of the monthlyelectric energies and the monthly amount of recovered water-heat energyin image because the supplied electric energies and the amount ofrecovered water-heat energy are displayed corresponding to theconceptual diagram.

The period of the comparison is not limited to each month, and it may beeach day or each year.

As mentioned above, since the cogeneration system using the electricpower generator set 1′ is provided with the image-displaying means,i.e., the display 32 displaying various calculated data concerning thevalues of the electric powers and the water-heat energy in charts, auser can be informed of the cost merit easily in no need of complicatedcalculation.

Further, since the system is provided with the means for calculatingfuel consumption for driving the engine and the image-displaying means,i.e., the display 32 which displays the respective electric energies andthe fuel consumption in a table, a user can be satisfied with such aneffect of the system that he or she can further accurately grasp theunit cost of electric power generated by the generator and the unit costof the water-heat energy on the basis of the actual data.

The operation-and-display unit 28 serving as the input/output means ofthe control unit 5 can be used as output means for taking out each ofthe above-mentioned data from the electric power generator set 1′.

In this regard, the operation-and-display unit 28 has a mechanism foroutputting to an IC card (card-like device) 33 serving as data-storagemeans, and a mechanism for outputting to a printer 34 serving asdata-registering means. Therefore, each of the above-mentioned data canbe memorized in the IC card 33, and numerical information of each of theabove-mentioned data and the above-mentioned diagrams (such as FIGS. 9to 14) can be printed by the printer 34.

Due to the above construction, each of the above-mentioned data can becollected by the IC card 33 so as to be read by a device which is notnetworked with the electric power generator set 1′. Especially if acomputer reads the data from the IC card 33 and the computer stores adata processing program different from those stored in the control unit5 and operation-and-display unit 28, the data processing can enhancevariation of electric power management.

The printer 34 can print the numerical information of each of theabove-mentioned data and the above-mentioned diagrams. Namely, due toeach of the above-mentioned data registered by the data-registeringmeans, the user can check change of electric power supply and electricenergy at the place of the operation-and-display unit 28. Especially inthe case of providing the printer 34, the printer 34 can serve as mainmeans for checking the data and diagrams thereof, whereby a small liquidcrystal display, for example, can be used as the display 32 so as toreduce costs thereof.

The system using the electric power generator set 1′ has means fordetecting and warning abnormalities of the system on the basis of thecalculated results.

In this regard, an abnormality detection program is stored in thecontrol unit 5 or the operation-and-display unit 28 in the controlsystem 2, or in the personal computer 35 or the supervisoryoperation-and-display unit 29 disposed outside the generator, so as towarn unexpected accidents and fault of the devices to a conservationaladministrator (a user, a maker or a third person doing conservation andadministration) in an instant, thereby enabling quick action againstabnormalities.

For example, the value of the water-heat energy relative to the value ofthe generated electric power does not change greatly unlessabnormalities occur in the devices. However, if the entrance sidethermometer 44, the exit side thermometer 45 or the flowmeter 46 breaksdown, the value of the water-heat energy becomes abnormally large orsmall, or is not displayed. Also, if sediments adhere to the inner wallof the primary cooling water passage 8 or the secondary cooling waterpassage 42 in the heat exchanger 41, the flux detected by the flowmeter46 becomes small, the entrance side temperature T1 becomes abnormallylarge, or the rotation frequency of the radiator fan 7 a increases so asto prevent abnormal temperature rise of the primary cooling water.

The abnormality detection program always supervises magnitudes of thedetected data and calculated data and balance of magnitude between thedata so as to detect abnormalities of the generator in an instant.

An alarm device 48 is disposed on the outer surface of the generator orat a position distant therefrom and connected to the generator with awire or on radio (preferably, disposed near the conservationaladministrator). When an abnormality is detected, the alarm device 48 istripped, and the operation-and-display unit 28 or the device outside thegenerator, i.e., the personal computer 35 or the supervisoryoperation-and-display unit 29, displays a probable troubled part orparts, thereby urging a quick measure. The alarm device 48 may have anymeans for stimulating any of the human's five senses, such as sound,light or vibration.

In this way, the cogeneration system using the electric power generatorset 1′ has the means for detecting abnormalities, which is a programstored in the control unit 5 or the operation-and-display unit 28 in thecontrol system 2, or stored in the personal computer 35 or thesupervisory operation-and-display unit 29 outside the generator. Thecogeneration system also has the means for warning abnormalities, whichare the alarm device 48 and any of the operation-and-display unit 28 andthe personal computer 35 or the supervisory operation-and-display unit29 disposed outside the generator.

As a result, the electric power generator set 1′ is ready to have aquick action against failures therein, thereby being advantageous in itssafety for a user having little knowledge of machinery, and in itsminimization of reduction of energy cost merit caused by breakdownthereof.

With regard to controlling of the electric power generator set 1′, auser can always control it and change the driving condition of theelectric power generator set 1′ in the vicinity thereof or a placedistant therefrom. Further, the electric power generator set 1′ may beso constructed that several typical programs of possibly frequentdriving patterns are prepared in a control system 2 so that a user canchoose one of the programs corresponding to operation status. Otherwise,a program of learning function may be stored so that driving conditionmay be controlled automatically so as to reduce an ecological burden orthe total electric power cost on the basis of operation status of theuser.

As mentioned above, the cogeneration system using the electric powergenerator set 1′ has the control system 2 serving as the controllingmeans for minimizing the ecological burden or the total electric powercost on the basis of the calculated results.

Therefore, a user can be satisfied with the cogeneration system whichcan be used in an optimal condition for his/her method and purpose ofuse thereof in no need of complicated calculation.

Next, explanation will be given on an electric power system constructedby connecting a plurality of electric power generator sets in parallelas a third embodiment of the present invention.

Firstly, explanation will be given on an entire construction of thiselectric power system 101 according to FIG. 15. The electric powersystem 101 comprises a plurality of electric power generator sets 102and a control system 110. Each pair of neighboring electric powergenerator sets 102, i.e., each pair of neighboring later-discussedcontrol units 105 are mutually connected through communication lines 103for communication of control signals and various data. In thisembodiment, the communication lines 103 adopt the multidrop typeconnection facilitating for easy extension of the electric powergenerator sets 102.

In the electric power system 101, each of the electric power generatorsets 102 connects its output side to electric power transmission lines109 so as to interconnect to a commercial electric power supply 40serving as an external electric power supply. Accordingly, thecommercial electric power and the generated electric power are suppliedto loads 126 connected to the electric power transmission lines 109.

A construction of each electric power generator set 102 will bedescribed in accordance with FIG. 16. Each electric power generator set102 has an engine 106, a generator 107, inverters 108 and the controlunit 105. The control unit 105 and the inverters 108 constitute acontrol system controlling drive of the electric power generator set102.

The engine 106 is connected to the generator 107 so as to drive thegenerator 107.

The engine 106 is connected to the control unit 105 including an enginecontroller through a control line 114 so that output of the engine 106is controlled on the basis of command from the control unit 105.

Additionally, the engine 106 may introduce cooling water thereinto so asto take out heat generated in the engine 106 with the cooling water. Inthis case, the electric power system 101 is used as so-calledcogenerator.

The inverters 108 are connected to an output side of the generator 107so that alternating current outputted from the generator 107 isconverted into direct current and inputted into the inverters 108.

The inverter 108 comprises a controller 123 (see FIG. 17) forcontrolling the frequency of alternating current, and for monitoring thevoltage and current of electric power inputted from the generator 107and the voltage and current of its output electric power, and theelectric energy.

In the construction shown in FIG. 16, two inverters 108 are connected toeach generator 107 so that each inverter 108 supplies electric powerindividually. Such a multiple inverters 108 enables individual outputcontrol of each inverter 108, thereby flexibly corresponding to changeof load.

One of the control units 105 serves as a master unit for centralizedcontrol over the other control units 105 so as to control drive/stop ofits own generator 102 or each of the other generators 102. The functionas the master unit is built in each of the control units 105. Eachcontrol unit 105, if one of the other control units 105 functions as themaster unit, follows the control unit 105 as the master unit, and ifneeded, it can be selected as the master unit to control the othercontrol units 105.

Accordingly, while the control unit 105 disposed in each electric powergenerator set 102 communicates with the control units 105 disposed inthe other electric power generator sets 102 through the communicationlines 103, one of the control units 105 is optionally selected as themaster unit to cooperatively control all the other control units 105. Inthis embodiment, the communication lines 103 adopt the multidrop typeconnection facilitating for easy extension of the electric powergenerator sets 102.

Various communication lines in FIG. 16 will be described.

The communication lines 103 connects the control units 105 in all theelectric power generator sets 102 to each other, thereby enablingcommunication of control information among the control units 105.

In each electric power generator set 102, communication lines 112connect the inverters 108 with the control unit 105 so as to transmitcontrol signals and signals indicating a status of the inverters 108between the inverters 108 and the control unit 105.

Communication lines 113 connect the inverters 108 in each electric powergenerator set 102 to the inverters 108 in the other electric powergenerator sets 102, thereby enabling communication of control signalsconcerning output control of the inverters.

Signal lines 115 are extended from current detectors 111 and connectedto the inverters 108 disposed in each electric power generator set 102so as to detect current value of the commercial electric power system ineach inverter 108.

A construction of the inverter 108 will be described in accordance withFIG. 17.

Each of the inverters 108 is provided with the controller 123, arectifying circuit 124, an output control part 125 and a communicationpart 121.

The rectifying circuit 124 converts alternating current of the electricpower generated by the generator 107 into direct current. The outputcontrol part 125 is supplied with the direct current electric power,converts it into alternating current and outputs it.

The controller 123 is connected to the output control part 125 so as tocontrol the electric power outputted from the output control part 125.

The controller 123 is connected to the communication part 121, to whichthe above-mentioned communication lines to the respective inverters 108can be connected so as to enable communication of the correspondinginverter 108 with the inverters 108 disposed in the other electric powergenerator sets 108, with the control unit 105 in the same electric powergenerator set 102, and detection of electric current from the commercialelectric power system.

The communication part 121 and communication lines will be described asfollows.

The communication part 121 has input/output connection ports 122 aconnected to the communication lines 112 so as to enable communicationof the corresponding inverter 108 with the control unit 105 in the sameelectric power generator set 102.

The communication part 121 has input/output connection ports 122 bconnected to the communication lines 112 so as to enable communicationof the inverter 108 in the same electric power generator set 102 witheach other and communication thereof with the inverters 108 in the otherelectric power generator sets 102.

The communication part 121 has input/output connection ports 122 cconnected to the signal lines 115 so as to connect the correspondinginverter 108 with the current detectors 111. Therefore, one of theinverters 108 can be optionally selected to detect the electric currentfrom the commercial electric power system.

A wiring construction among the inverters will be described inaccordance with FIG. 18.

In each electric power generator set 102, the control unit 105 isconnected to the inverters 108 through the communication line 112.

All the inverters 108 are connected with one another through thecommunication lines 113 so as to transmit output control informationamong all the inverters 108.

The signal lines 115 connect each inverter 108 with the other inverters108, and the current detectors 111 are disposed at the upstream side ofa joint of the electric power transmission line 109 to the loads 126 tothe commercial electric power supply 40 and the signal line 115 of themost upstream inverter 108 in the most upstream electric power generatorsets 102 (toward the commercial electric power supply 40). Therefore,one of the inverters 108 can be optionally selected so as to enabledetection of the electric current from the commercial electric powersystem. Current transformers or the like can be used as the currentdetectors 111.

FIG. 18 does not illustrate all the inverters 108 connected to thesignal lines 115. However, all the inverters 108 are actually connectedto the current detectors 111 through the signal lines 115.

In this way, in the electric power system 101, the inverters 108 in allthe electric power generator sets 102 can detect the electric currentfrom the external electric power system. Therefore, it is possible thatonly the troubled electric power generator set 102 having abnormality inits detected current value is stopped and maintained while the otherelectric power generator sets 102 are kept in interconnection with oneanother without stopping, and that all the electric power generator sets102 can be equaled in their cumulative drive times.

Further, as mentioned above, one of the inverters 108 serves as themaster unit for centralized control over the other inverters 108 so asto control the generated electric output of itself or the others. Thefunction as the master unit is built in all the inverters 108. Eachinverter 108, if one of the other inverters 108 functions as the masterunit, follows another inverter 108 as the master unit, and if needed, itcan serve as the master unit for centralized control over the otherinverters 108.

In the present embodiment, the communication lines 103, 112 and 113adopt multidrop type connection so as to facilitate for easy extensionof the electric power generator sets 102.

Next, explanation will be given on a control method of theabove-mentioned electric power system 101 for distribution of electricpower supply.

With regard to the present control, one of the inverters serves as themaster unit cooperatively controlling the other inverters. The inverterserving as the master unit accumulates information concerning generatedelectric outputs required for the other respective inverters, calculatestotal generated output required for the whole electric power system, anddetermines the number of the electric power generator sets to be drivenon the basis of the calculated result.

The present control is represented by a flow chart 500 of FIGS. 19 and20. The present control according to the flow chart 500 will bedescribed as follows.

Each inverter 108 detects electric current from the commercial electricpower system by the current detector 111 so as to calculate a commercialsupply electric power R [W] in the electric power transmission line 109from the commercial electric power supply 40 (a step 301).

The inverters 108 calculate their respective outputs a, b, c, . . . [W](a step 302). Namely, the outputs a, b, c, . . . [W] are observationalelectric power outputs of the respective inverters 108. On the otherhand, hereafter, rated (maximum) outputs of the inverters 108 arereferred to as rated outputs A, B, C, . . . [W].

Then, arbitrary one of the inverters 108 as the master unit(hereinafter, referred to as a “master inverter 108”) accumulates dataof the observed outputs a, b, c, . . . from the other inverters 108 andcalculates the observed total value t [W] of the outputs a, b, c, . . .(a step 303). Alternatively, each control unit 105 may accumulate dataof output of the corresponding inverters 108 in each electric powergenerator set 102.

When the electric power system 101 is used as an interconnection systemwithout reverse electric power flow, the master inverter 108 cooperateswith the other inverters so as to control their generated output toprevent reverse flow of electric power from the electric power system101 to the external electric power supply.

The master inverter 108 controls output thereof or of the otherinverters as the above so as to prevent the reverse electric power flow(a step 304). This step can be arbitrarily set into the program of thecontrol unit 105 so that a user can select whether the reverse electricpower flow is allowed or prevented. After the control for prevention ofthe reverse electric power flow, the detection of output electric powerrestarts.

Next, the control unit 105 as the master unit (hereinafter, referred toas a “master control unit 105”) monitors the total value t [W] from themaster inverter 108 (a step 305). Alternatively, the master control unit105 may monitor the total value t [W] obtained by totaling all the dataaccumulated by the respective control units 105.

Then, the control unit 105 checks whether the above obtained total valuet [W] agrees with a total value T [W] of the rated outputs A, B, C, . .. of the electric power generator sets 102 under operation or not (astep 306).

By this check, it is checked whether the whole electric power system 101demonstrates the highest performance or not, that is, whether the outputelectric power of the electric power generator sets 102 under operationreaches the maximum or not.

When the total value t [W] agrees with the total value T [W], it isconsidered that the output of the electric power generator sets 102under operation reaches the maximum, that is, the whole electric powersystem 101 is operated to output its maximum electric power, therebydropping the following control.

On the other hand, when the total value t [W] is smaller than the totalvalue T [W], the master control unit 105 selects either a program (aroute R1) of operating the counted electric power generator sets 102(determined in number as the above) equalized in output or a program (aroute R2) of operating specific electric power generator sets 102 withtheir maximum output (a step 307).

Namely, a user can select either the program of operating the countedelectric power generator sets 102 equally in output (the route R1) orthe program of operating the specific electric power generator sets 102fully in output supported by another electric power generator set 102compensating for shortage of output (the route R2).

Of the two, firstly, the program of operating all the counted electricpower generator sets 102 equally in output will be described.

The present program (the route R1) forcibly equalizes outputs of theinverters of all the counted electric power generator sets 102.

Firstly, the number of the electric power generator sets 102 to beoperated equally in output is determined, and the electric powergenerator sets 102 to be operated (the electric power generator setsintending to operate) are chosen (some of the electric generators 102are counted to be operated) (a step 308).

The count and choice of devices depends on calculation of theaccumulated operation time of each electric power generator set 102 for“equalizing the accumulated operation times of the respective electricpower generator sets 102”, for “rest of the electric power generatorsets 102 at the time of maintenance following the schedule ofmaintenance”, or for the like. In this way, the electric power generatorsets 102 are controlled by the corresponding control units 105 to beshifted in operation at each established period.

The rest electric power generator set 102, if it exists, is also countedas a target to be operated.

According to the count and choice, any of the operated electric powergenerator sets 102 may be shut down. It means selection of the electricpower generator set 102 to be rest (a step 309).

Then, it is checked whether the inverter 108 in the electric powergenerator set 102 to be rest serves as the master unit or not (a step310).

If the inverter 108 in the electric power generator set 102 to be restserves as the master unit, the function of the master unit is shifted toanother inverter 108 in the electric power generator set 102 to beoperated (a step 311).

Furthermore, it is checked whether the control unit 105 in the electricpower generator set 102 to be rest serves as the master unit or not (astep 312).

If the control unit 105 in the electric power generator set 102 to berest serves as the master unit, the function of the master unit isshifted to another control unit 105 in the electric power generator set102 to be operated (a step 311).

In addition, preferably, each control unit 105 monitors theoperation/rest state of the corresponding electric power generator set102 or of the other electric power generator sets 102, and if thecontrol unit 105 and the inverter 108 in the same electric powergenerator set 102 serve as the master units, the control unit 105automatically shifts the functions thereof and of the correspondinginverter 108 as the master units to the control unit 105 and theinverters 108 in another electric power generator set 102 underoperation.

According to the above steps 309 to 313, before shutting down of theelectric power generator set 102 having the control unit 105 and theinverter 108 serving as the master units, the functions as the masterunits are shifted to the control unit 105 and the inverter 108 inanother electric power generator set 102.

Accordingly, the inverter 108 of one of the electric power generatorsets 102 under operation is set as the master unit to cooperativelycontrol the other inverters 108, and then, the operating electric powergenerator set 102 counted to be rest is shut down and the rest electricpower generator set 102 counted to be operated starts (a step 333).

Next, the program of operating the specific electric power generatorsets 102 fully in output supported by another electric power generatorset 102 compensating for shortage of output will be described.

This present program forcibly operates the specific electric powergenerator sets 102 fully in output, and operates one of the otherelectric power generator sets 102 so as to make output of its invertercorrespond to change of the commercially supplied electric power R [W].

Firstly, the number of the electric power generator sets 102 to be fullyoperated in output is determined, and the fully operated electric powergenerator sets 102 and the electric power generator set 102corresponding to change of the commercially supplied electric power R[W] (the electric power generator sets 102 to be operated) are chosen (astep 320).

The count and choice of devices depends on calculation of theaccumulated operation time of each electric power generator set 102 for“equalizing the accumulated operation times of the respective electricpower generator sets 102”, for “rest of the electric power generatorsets 102 at the time of maintenance following the schedule ofmaintenance”, or for the like. In this way, the electric power generatorsets 102 are controlled by the corresponding control units 105 to beshifted in operation at each established period.

The rest electric power generator set 102, if it exists, is also countedas a target to be operated.

According to the count and choice, any of the operated electric powergenerator sets 102 may be shut down. It means selection of the electricpower generator set 102 to be rest (a step 309). The hereafter flow (thesteps 309 to 333) is the same as the above program for equal outputcontrol.

Accordingly, the control system (control unit 105) serving as the masterunit collects and accumulates data from the other control systems(control unit 105) concerning the generated electric powers required forthe respective electric power generator sets 102, so as to calculate theload electric power of electric power system 101, thereby determiningthe number of the electric power generator sets 102 to be operated.

In this way, either the equal-output control or the full-output controlof the specific electric power generator sets 102 can be selected, andthe accumulated operation time of each electric power generator set isequalized.

According to the above flow, each electric power generator set 102 isswitched between the operating state and the rest state.

Herein, explanation will be given on features of the above-mentioned twocontrols (the routes R1 and R2).

With regard to the equal output control (the route R1), the control unit105 of the electric power generator set 102 serving as the master unitcontrols its electric power generator set 102 and the other electricpower generator sets 102 so as to bring equalization of outputs of thetarget electric power generator sets 102 to be operated intoconsideration for determination of the number of operated generators.

Accordingly, all the electric power generator sets 102 are equalized intheir operation times in no need of excessive operation and output,thereby prolonging a life of whole electric power system 101.

On the other hand, with regard to the full-output control of thespecific electric power generator sets 102 (a route R2), the controlunit 105 of the electric power generator set 102 serving as the masterunit controls its electric power generator set 102 and the otherelectric power generator sets 102 so as to bring maximization of outputsof the (several) target electric power generator sets 102 to be operatedinto consideration for determination of the number of operatedgenerators.

Accordingly, the specific electric power generator sets 102 are operatedfully in output so as to demonstrate the best performance (operate inhigh efficiency). Furthermore, the electric power generator sets 102 tobe rest may be chosen among the electric power generator sets 102 underoperation.

For example, when the maximum output of one electric power generator set102 is 10 [kW], the commercially supplied electric power R [W] is 40[kW], and outputs of five electric power generator sets 102 are 8 [kW],7 [kW], 9 [kW], 8 [kW] and 8 [kW] respectively, outputs of four electricpower generator sets 102 are set to the maximum output 10 [kW] so as tocompensate 40 [kW] with the total thereof, thereby resting the oneremaining electric power generator set.

In each of these controls (the routes R1 and R2), the control system(control unit 105) serving as the master unit may switch the electricpower generator sets 102 under operation at each established period.Namely, the target electric power generator sets 102 to be operated arechosen on the basis of the history of operation time so as to equalizeoperation times of all the electric power generator sets 102, wherebythe accumulative operation time of the specific electric power generatorset 102 is prevented from becoming longer than those of the otherelectric power generator sets 102 so as to prolong a life of wholeelectric power system 101.

In each of the two controls (the routes R1 and R2), the function as themaster unit is shifted between the inverters 108, and between thecontrol units 105.

According to the program, when the inverter 108 and the control unit 105as the master unit are decided to be rest, the function is shifted toanother inverter 108 and control unit 105 so as to maintain the generalcontrol necessary for the whole electric power system 101.

Therefore, when a certain electric power generator set 102 requiresmaintenance while the electric power system 101 remains ininterconnection, only the requiring electric power generator set 102 canbe rest instead of rest of the other electric power generator sets 102.

Furthermore, the inverter 108 as the master unit must constantly detectthe value of electric current from the commercial electric power systemso as to ensure the interconnection. In this regard, the inverters 108of all the electric power generator sets have abilities of detecting thecurrent value, whereby the current value never becomes impossible to bedetected even if the specific electric power generator set 102 rests.

Conventionally, only an inverter of one specific electric powergenerator set detects the value of current from the commercial electricpower system so that the electric power generator set 102 to be restcannot be chosen freely. However, with regard to the presentconstruction, the inverters 108 of all the electric power generator sets102 can function as the master unit so that the target electric powergenerator set 102 to be rest can be chosen freely.

Therefore, even the specific electric power generator set 102 can berest for maintenance without making any of the other power generators102 rest, so that the operation times of all the electric powergenerator sets 102 can be equalized.

By the above sequence control flow, the control unit 105 automaticallydetermines operation/rest of the electric power generator sets 102.Alternatively, a user may optionally choose the target electric powergenerator sets 102 to be operated or rest.

For example, in the step 307 (selection of control method) of the flowchart 500 in FIG. 19, a user may alternatively specify one of theelectric power generator sets 102 to be stopped for maintenance.

Industrial Applicability

The present invention is applicable to an electric power supply systemcomprising a electric power generator set, which includes a generatordriven by an engine and an inverter having an ability of interconnectingwith an external electric power supply. A typical external electricpower supply system is a commercial electric power supply from aelectric power plant, any electric power supply system may serve as theexternal electric supply system if it can interconnect with an outputelectric power system line of the electric power generator set. Theelectric power generator set may supply commercial electric power. Theelectric power generation system of the present invention provides sucha satisfying system of managing electric power supplies for usersbecause of use of the image-displaying device for users' easy graspingof the state of used electric power, and provides a plurality ofelectric power generator sets each of which has high all-around abilityto be used, thereby contributing in the reduction of cost, or forvarious convenience. The present invention is also applicable toconstruction of a compact electric power system or cogeneration systemwhich recovers waste heat of the electric power generator set.

1. An electric power system comprising a plurality of electric powergenerator sets, each of the electric power generator sets comprising: anengine; a generator driven by the engine; an inverter having an abilityof interconnecting the generator with an external power supply; meansfor detecting information concerning electric power from the externalpower supply and electric power from the electric power generator set;means for calculating electric power and energy from the external powersupply, electric power and energy from the power generator set, andelectric power and energy to a load; means for recording each of thecalculated electric powers and energies; and a control system forcontrolling output of the generator, wherein the electric power systemis constructed by interconnecting the control systems with each other,and one of the control systems serving as a master unit comprises meansfor accumulating information on generated power required of the otherpower generator set(s), the information being transmitted from the othercontrol system(s) of the other power generator set(s); calculating theload electric power of the electric power system; and determining thenumber of the power generator sets to be operated.
 2. The electric powersystem as set forth in claim 1, wherein each of the power generator setscomprises: image-displaying means for displaying a diagram of eachelectric energy of the external power supply, the power generator setand the load.
 3. The electric power system as set forth in claim 1,wherein each of the power generator sets comprises: means forcalculating fuel consumption of the engine, and image-displaying meansfor displaying each of the electric energy and the fuel consumption in atable.
 4. The electric power system as set forth in claim 1, whereineach of the power generator sets comprises: means for externallytransmitting a result calculated by said calculating means.
 5. Theelectric power system as set forth in claim 1, the power generator setsbeing connected in parallel, wherein each of the power generator setscomprises: means for controlling its own generator and invertercooperatively, and means for detecting current value from the externalpower supply.
 6. The electric power system as set forth in claim 5,wherein the control system of each of the power generator setscomprises: means for communicating with the control system of the otherpower generator sets, and means for centralized control over the othercontrol systems so as to enable the control systems to serve as themaster unit.
 7. (canceled)
 8. The electric power system as set forth inclaim 1, wherein the control system serving as the master unitcomprises: means for controlling the counted power generator sets to beoperated so as to equalize their outputs.
 9. The electric power systemas set forth in claim 1, wherein the control system serving as themaster unit comprises: means for controlling specific one of the countedpower generator sets to be operated so as to maximize output thereof.10. The electric power system as set forth in claim 1, wherein thecontrol system serving as the master unit comprises: means forrecognizing operation/rest state of its own power generator set or theother power generator set(s) and choosing a control system serving as anext master unit.
 11. The electric power system as set forth in claim 1,wherein the control system serving as the master unit comprises: meansfor shifting the power generator set to be operated at eachpredetermined period.
 12. The electric power system as set forth inclaim 1, wherein the control system serving as the master unitcomprises: means for preventing reverse power flow to the external powersupply by cooperating with the other control system(s).
 13. A systemcomprising a power generator set comprising: an engine; a generatordriven by the engine; an inverter having an ability of interconnectingthe generator with an external power supply; means for detectinginformation concerning electric power of each of the external powersupply and the power generator set; means for calculating electric powerand energy of each of the external power supply, the power generator setand a load; means for recording each of the calculated powers andelectric energies; and waste heat recovery means for recovering wasteheat from the engine so as to generate heat; means for detectinginformation concerning heat energy consumed for generating hot water;means for calculating the heat energy, an amount of the heat energy andenergy efficiency; means for recording a result calculated by said meansfor calculating the heat energy; and image-displaying means fordisplaying each electric power of the external power supply, the powergenerator set and the load of the system, the amount of heat energy, andthe energy efficiency in a table.
 14. The system as set forth in claim13, further comprising: means for calculating fuel consumption fordriving the engine; and image-display means for displaying each of theelectric energy, the heat energy, and the fuel consumption in a table.15. The system as set forth in claim 13, further comprising: means forexternally transmitting the calculated result.
 16. The system as setforth in claim 13, further comprising: means for remote communication toenable the system to be operated remotely.
 17. The system as set forthin claim 13, further comprising: means for detecting abnormality of thesystem based on the calculated result and informing about theabnormality.
 18. The system as set forth in claim 13, furthercomprising: means for minimizing ecological load or power cost based onthe calculated result.
 19. A method of generating power using aplurality of electric power generator sets, each comprising: an engine;a generator driven by the engine; and an inverter having an ability ofinterconnecting the generator with an external power supply, said methodcomprising: (I) operating each electric power generator set by:detecting information concerning electric power from the external powersupply and electric power from the electric power generator set;calculating the electric power and energy from the external powersupply, the electric power and energy from the power generator set, andelectric power and energy to a load; recording each of the calculatedelectric powers and energies; and controlling output of the generator bya control system; (II) interconnecting the control systems with eachother, wherein one of the control systems serves as a master unit; and(III) operating the master control system by: accumulating informationon generated power required of the other power generator set(s), saidinformation being transmitted from the other control system(s) of theother power generator set(s); calculating the load electric power of theelectric power system; and determining the number of the power generatorsets to be operated.
 20. A method of generating power using a powergenerator set comprising: an engine; a generator driven by the engine;and an inverter having an ability of interconnecting the generator withan external power supply, said method comprising: detecting informationconcerning electric power of each of the external power supply and thepower generator set; calculating electric power and energy of each ofthe external power supply, the power generator set, and a load;recording each of the calculated powers and electric energies; andrecovering waste heat from the engine so as to generate heat; detectinginformation concerning heat energy consumed for generating hot water;calculating the heat energy, an amount of the heat energy, and energyefficiency; recording the calculated results; and displaying eachelectric power of the external power supply, the power generator set,and the load, the amount of heat energy, and the energy efficiency in atable.